docs(friction): escalate execution-mode prompt; no plan→impl approval gate

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/FRICTION.md

@@ -77,3 +77,20 @@ earning its keep.
     ADR's Deferred list** in the same change. Three hits now — promote from "worth a
     check" to **build it**: a `/review-repo` rule flagging any ADR "Deferred/Open" entry
     whose subject is named as RESOLVED/DECIDED elsewhere.
+
+## 2026-06-06
+
+- `[recurring]` **Asked the execution-mode question AGAIN** ("subagent-driven vs inline —
+  which approach?") at the end of `writing-plans`, despite the 2026-06-05 standing
+  preference *and* the `always-subagent-driven-execution` memory both saying don't ask.
+  Root cause: the `writing-plans` skill's "Execution Handoff" step scripts the menu, and
+  I followed the skill text over the user's standing override. Second occurrence →
+  escalate from "skip the prompt" to a **hard rule**: never present the execution-mode
+  menu; finishing a plan means defaulting straight to subagent-driven.
+- `[friction]` **Don't pause for approval between writing a plan and implementing it.**
+  The user has standing pre-approval to carry straight through plan → implementation. The
+  brainstorming/plan flow already has explicit approval gates (design approval, spec
+  review); adding another "shall I proceed to implement?" gate after the plan is written
+  is redundant friction. → After `writing-plans` finishes, begin subagent-driven
+  implementation directly. The only reason to stop is a genuine blocker or ambiguity, not
+  a routine checkpoint.